i know that european colonialism largely collapsed after WW2, but not how or why exactly.

im not sure what you mean by politics exactly. the french revolution for instance was ignited by the crushing oppression of the peasantry by the monarchy - more of a social movement, than a political one.

Is yours a historical piece or are just trying to better understand imperialism?

That is the kind of topic you could spend decades studying....I guess I'd recommend starting with reading up on Post-colonial Theory, people like Edward Said, Gayatri Chakravorty Spivak, and going back further, Hegel, Fanon and Sartre.

But seriously, unless you narrow your focus a bit more, you're going to have a hard time finding suitable resources.

What I mean is that I wanted to learn the politics / how the collapse of Imperialism and all happened post-WW2. Specifically, Africa and maybe South America. Like the reasoning of the rebellions and what was going on at home that kept the imperial power from just reinforcing the colony, or switching their tactics and all.

Then the social conditions, politics etc. that caused Monarchies in Europe to pretty much...disappear from the French revolution to post-WW1.